The release reveals some new features in the software but leaves questions about the upgradability of current devices

Google on Tuesday released an SDK for Android 2.0, revealing some new features that will come with the upgraded mobile operating system.

The news comes a day before a Verizon event in New York City that will introduce the operator's first Android phone, which will run Android 2.0. However, the upgrade path for existing Android phones, and some that are soon to go on sale, is uncertain.

Android 2.0 includes a number of new features, such as digital zoom on the camera, multi-touch control, and an e-mail inbox that combines messages from multiple accounts.

The new Quick Connect feature will let users touch the photo of a person in the contact list and then select call, text or e-mail from a menu. It is designed to make it easy for users to communicate with contacts.

The feature is a welcome addition, said Avi Greengart, an analyst with Current Analysis. "The knock on Android has been that it's boring. The UI's whole functionality is not as polished as what you get on WebOS, iPhone, or even Android with third-party overlays like the HTC Sense," he said. Sense is a user interface that HTC developed for some of its Android phones.

Android 2.0 also includes Exchange support. Android users have been able to get e-mail from Exchange in various ways, including through third-party applications or support provided by the hardware vendor. With the latest version of the operating system, Exchange support is built in, although Google specifically notes that handset makers can choose whether to include Exchange.

Google has also updated the Android mobile Web browser, with support for a quartet of APIs (application programming interfaces) from the emerging HTML 5 standard. That's significant because now browser-based applications can act much more like native applications. For example, the HTML 5 Database API supports client-side databases using SQL, to store data such as Web e-mail messages locally. This is now a feature of the browser in Android 2.0. In addition, the HTML 5 Application Cache lets developers store application functions and the UI, in JavaScript and Cascading Style Sheets, so users can access them offline.

Other browser improvements include: the HTML 5 Geolocation API, opening up information on the device's location; support for full-screen video; a new URL bar that users can tap for instant searches and navigation; bookmarks outfitted with Web page thumbnails; and double-tap zoom.

While Verizon's Droid phone will run Android 2.0, it's uncertain which other recently introduced or currently available phones will be able to use the software. For example, Motorola's Cliq, expected to go on sale in early November, runs Android 1.5. It's unclear whether users will be able to upgrade the phone to Android 2.0.

Google said it's up to carriers and handset makers. "Because Android is open source, all software updates we release are available for carriers and handset makers to take and update their current or future Android-powered devices," Katie Watson, a Google spokeswoman, said via e-mail. Past updates to the operating system have been automatically pushed out to the few available models.

It's possible that hardware requirements could prevent some devices from upgrading to the newest software. In addition, Greengart wonders if users of devices such as the Cliq or the Sense, with custom user interfaces, would have to also update the user interface after receiving the new operating system.

Motorola and T-Mobile, which will sell the Cliq and offers two other Android phones, did not reply to questions about whether their phones would be upgradable to the new version.